Calibration of Reactive Transport Models for Remediation of Mine Drainage in Solid-Substrate Biocolumns

Abstract

Experimental data pertaining to two pairs of solid-substrate sulfate-reducing biocolumns for remediation of mine drainage were used for calibrating and testing new reactive transport models based on sulfate reduction and sulfide precipitation linked to rate-limiting solid-substrate hydrolysis. First-order ͑F͒ and Contois ͑C͒ kinetics for decomposition as well as different numbers of pools of decomposable materials were proposed in different models ͑F1-F3 and C1-C3͒. Effluent sulfate concentrations for one of the columns were used as the basis for calibrating the different models and, due to limitations in the calibration data set, the number of adjustable model parameters was limited using parameter tying. Calibrated models were ranked using Akaike information criterion, and Model C2, followed by Model C1, based on Contois kinetics, emerged as the models that were supported to a greater extent by the data. For an independent experimental data set, model testing was performed using Models C2 and C1 with parameters from the previous calibration resulting in good approximations of effluent sulfate. For the calibration data set, longer-term model predictions for effluent sulfate, decomposable substrates, and microbial populations also were performed. The reactive transport models represent a potentially valuable tool for the design of solid-substrate bioreactors used for the treatment of mining influenced water, although future model validation using longer-term field data sets will be necessary to confirm the model predictions.